Hi. I have an account with IB and with a pro firm. I have been experimenting with options spreads-calendars ,flies,etc where I enter a limit on Ib and an identical limit with my other platform from Merrill. I've been doing it past 2 weeks and find that out of the 20 or so orders I've put in, the IB gets executed first with the ML platform executing about 10 of the orders w the remaining 10 being unexecuted. Someone told me the reason is that the Ml order is a BD order which is ignored. I thought that practice was done 3-5 years ago wherein customer orders-being percieved as dumb $ gets executed first. Has anyone experienced the same.? Furthermore, has anyone compared equity option spread execution between retail IB vs. retail Thinkorswim. Thanks in advance.